This invention relates to an electrophotographic reproducing apparatus and more particularly to a charge-erasing device for use in an electrophotographic apparatus in which an image of a suitable reproduction size is formed by exposure to a pattern of light.
In general, with the electrophotographic reproducing apparatus of the type described, a charging device operates continuously during rotation of a photosensitive body upon commencing a sequence of reproduction cycles, so that there is uniform charging not only of an image-forming portion of the surface of the photosensitive body, but also of the portion of the surface intermediate the aforesaid image-forming portion and a subsequent image portion, and (for narrow copy sizes) the nonimage-forming portions at both sides of the aforesaid image-forming portion. Thus, when such a charged surface is subjected to development, the nonimage-forming portions (i.e., those having no bearing on reproduction of the original) electrostatically attract toner, so that the amount of toner required therefor is used in vain and the load on a residual-toner cleaning device becomes excessive.
For this reason, there has been proposed a charge-erasing device in which a charge-erasing light source is located at the nonimage-forming portion between a charging station and an exposure station. By controlling the turn-on and turn-off operations of the charge-erasing light source in association with rotation of the photosensitive body, as well as the required reproduction size, one can erase charges previously deposited on the nonimage-forming portion as it passed the charging station. Such a device suffers from disadvantages, however, in that since a certain period of time is required for energizing the aforesaid charge-erasing light source to full power at the instant when illumination by the light source is desired, there accordingly results insufficient radiation of the light on the nonimage-forming portion although the intent is to have the charge thereon erased by means of the light source. Thus, there occurs a failure to completely erase the charge on the leading edge of the nonimage-forming portion.
The present invention is therefore directed to avoiding the above-mentioned shortcomings.